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Infection and Immunity, November 2009, p. 4714-4723, Vol. 77, No. 11
0019-9567/09/$08.00+0 doi:10.1128/IAI.00749-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
The Major Neutralizing Antibody Responses to Recombinant Anthrax Lethal and Edema Factors Are Directed to Non-Cross-Reactive Epitopes
,
Melissa L. Nguyen,1,2
Simon Terzyan,3
Jimmy D. Ballard,1
Judith A. James,4 and
A. Darise Farris1,2*
Department of Microbiology & Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104,1 Arthritis and Immunology Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104,2 Crystallography Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104,3 Clinical Immunology Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 731044
Received 1 July 2009/ Returned for modification 29 July 2009/ Accepted 24 August 2009
Anthrax lethal and edema toxins (LeTx and EdTx, respectively) form by binding of lethal factor (LF) or edema factor (EF) to the pore-forming moiety protective antigen (PA). Immunity to LF and EF protects animals from anthrax spore challenge and neutralizes anthrax toxins. The goal of the present study is to identify linear B-cell epitopes of EF and to determine the relative contributions of cross-reactive antibodies of EF and LF to LeTx and EdTx neutralization. A/J mice were immunized with recombinant LF (rLF) or rEF. Pools of LF or EF immune sera were tested for reactivity to rLF or rEF by enzyme-linked immunosorbent assays, in vitro neutralization of LeTx and EdTx, and binding to solid-phase LF and EF decapeptides. Cross-reactive antibodies were isolated by column absorption of EF-binding antibodies from LF immune sera and by column absorption of LF-binding antibodies from EF immune sera. The resulting fractions were subjected to the same assays. Major cross-reactive epitopes were identified as EF amino acids (aa) 257 to 268 and LF aa 265 to 274. Whole LF and EF immune sera neutralized LeTx and EdTx, respectively. However, LF sera did not neutralize EdTx, nor did EF sera neutralize LeTx. Purified cross-reactive immunoglobulin G also failed to cross-neutralize. Cross-reactive B-cell epitopes in the PA-binding domains of whole rLF and rEF occur and have been identified; however, the major anthrax toxin-neutralizing humoral responses to these antigens are constituted by non-cross-reactive epitopes. This work increases understanding of the immunogenicity of EF and LF and offers perspective for the development of new strategies for vaccination against anthrax.
* Corresponding author. Mailing address: Arthritis and Immunology Program, Oklahoma Medical Research Foundation, 825 NE 13th Street, Oklahoma City, OK 73104. Phone: (405) 271-7389. Fax: (405) 271-4110. E-mail: darise-farris{at}omrf.org
Published ahead of print on 31 August 2009.
Supplemental material for this article may be found at http://iai.asm.org/.
Infection and Immunity, November 2009, p. 4714-4723, Vol. 77, No. 11
0019-9567/09/$08.00+0 doi:10.1128/IAI.00749-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
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